There is some risk that these lights produce glare on wet surfaces, such as wet runways and/or taxiways, even if the lights are aimed downwards, i.e. below a horizontal plane. Glare is considered as a major contributing factor to loss of perception of speed and distance of the exposed individuals. Therefore there is some risk that glare contributes to ground incidents at bad weather. Reflections on wet surfaces further reduce the amount of light that actually hits the surface and the ground markings, which makes it much more difficult to see those markings.
It therefore would be beneficial to reduce these reflections and to increase the amount of light that becomes visible to aircraft pilots and members of the ground staff.